1. Field of the Invention
The embodiments described herein are directed to UWB systems and more a particularly to reducing interference between multiple piconets in a UWB system.
2. Background of the Invention
Recently Ultra Wide Band (UWB) has been promoted as a solution that can bring the convenience and mobility of wireless communications to many applications that require high-speed interconnections. Other conventional wireless communication technology is limited in that it cannot provide the high-speed interconnects required for many short-range wireless applications that can enable, e.g., connection of multiple devices for transmission of video, audio, and other high-bandwidth data, thus freeing people from the wires normally associated with such applications.
A conventional UWB system works by transmitting lots of short pulses across a very wide spectrum of frequencies up to several gigahertz in bandwidth. An UWB receiver then translates the pulses into data by listening for a familiar pulse sequence sent with the transmission. Conventional UWB is defined as any radio technology occupying a spectrum bandwidth that is greater than 20% of the center frequency, or a bandwidth of at least 500 megahertz. UWB combines the broad spectrum with low power to improve speed and reduce interference with other wireless spectra. As a result, UWB provides significant channel capacity over short ranges and limited interference with other systems operating in the same area.
While UWB promises to provide systems with data rates as high as 1 GHz, UWB systems are also envisioned that operate at lower data rates, such as data rates in the hundreds of megahertz. For example, one proposal defines a Frequency Division Multiplex (FDM) system that divides the available spectrum into three bands, with each band having a 500 MHz bandwidth. Preferably, multiple piconets would be able to operate within each band; however, use of such Simultaneous Operating Piconets (SOPs) can result in interference between the piconets. Further, it can be preferable to allow different types of devices to communicate with a given piconet. For example, it can be preferable that devices comprising coherent receivers as well as non-coherent receivers, and even differentially coherent receivers, to all communicate with the same piconet. This would allow users to trade-off cost versus performance in deciding what type of device to purchase and use. For example, if lower performance is acceptable, but cost is the driving issues, then the user could purchase a device including a non-coherent receiver. On the other hand, if performance is the driving factor, then the user would be free to purchase a better performing device, i.e., one that uses a coherent receiver.
Unfortunately, conventional UWB devices and technology are not capable of sufficiently limiting SOP interference, nor do they allow multiple devices to speak with the same piconet.